Method and apparatus for extrusion of workpieces

ABSTRACT

The invention relates to a method and apparatus for extrusion of workpieces. Especially the invention is concerned with a method and apparatus for extruding workpieces whereby a cooling medium is applied to transfer excessive heat from the apparatus in order to increase extrucion speed. The cooling medium applied in a gaseous state is further used to create a protective atmosphere at the downstream end of the apparatus to eliminate the oxidizing effects of normal air.

United States Patent [191 Wagner et al.

[ METHOD AND APPARATUS FOR EXTRUSION OF WORKPIECES [75] Inventors: Alfred Wagner, Steis slingen;

Juergen Hesse, Dusseldorf, both of Germany [73] Assignee: Swiss Aluminium Ltd., Chippis,

Switzerland [22] Filed: Mar. 15, 1972 211' Appl. No.: 234,703

[30] Foreign Application Priority Data Mar. 18, 1971 Switzerland.....'. 4014/71 [52] US. Cl. 72/269, 72/342 [51] Int. Cl BZld 37/16 [58] Field of Search 72/342, 269, DIG. l3, l3; 29/DlG. 47; 83/171 [56] References Cited UNITED STATES PATENTS 2,161,570 6/1939 Harris 72/13 [451 May 7,1974

3,673,904 7/1972 Cooper 83/171 Primary ExaminerCharles W. Lanham 1 Assistant Examiner-Robert M. Rogers Attorney, Agent, or Firm-Ernest F. Marmorek [5 7] ABSTRACT The invention relates to a method and apparatus for extrusion of workpieces. Especially the invention is concerned with a method and apparatus for extruding workpieces whereby a cooling medium is applied to transfer excessive heat from the apparatus in order to increase extrucion speed. The'cooling medium applied in a gaseous state is further used to create a protective atmosphere at the downstream end of the apparatus to eliminate the oxidizing effects of normal air.

2 Claims, 6 Drawing Figures PATENTEDIAY new I 3 808.865

7 sum 2 or 3 an N 5 PATENTEDMAY 71974 3.808.865

SHEET 3 BF 3 Fig.4 ','Fig.s" 1.9 1.7 so s1 52 1.9

I @iV/ZiW/Z METHOD AND APPARATUS FOR EXTRUSION OF WORKPIECES METHOD AND APPARATUS FOR EXTRUSION OF WORKPIECES The present invention relates-to a method and apparatus for extrusion of workpieces, especially of aluminium alloys.

The properties of workpieces formed out of aluminium and its alloys such as rods, tubes, etc., are substantially determined by two factors, namely the ingot or billet temperature and the speed of extrusion, which for creation of an economical production are in close relationship. A high ingot and billet temperature could appear to be employable from considerations relating to the press, especially for the reason that then a lesser deformation work need be exerted by. the press plunger on the ingot or billet in the receiver. An economical throughput or an optimum use of a press are however contradicted by the'low press speed then required. Thus with a high ingot or billet temperature which in itself saves deformation work, and an excessively high extrusion speed, one finds an insufficient pressure weld and thus a defective metal structure, which reduces the employment of workpieces made in this way. For ex ample in hollow extrusions, an insufficient pressure weld is especially harmfully noticeable, in that no welding is present of the metal streams which have been separated by a bridge. Starting from this, the ingot or billet is held at a temperature suitable for the deformation work of aluminium or an aluminium alloy and for a most efficient use of the press the press speed is increased. Principally the machines allow unlimited press speeds, however surface defects of .the workpieces excluding them from special usages 'put up an uppermost press speed boundary. So for instance a complete desintegration of the aluminiumoxide layer upon the surface of the extruded workpiece is to be observed released by an excessive deformation heat in the workpiece, produced by too high an extrusion speed. Then the workpiece is no longer usable for an eloxal quality. A similar surface defect is the so-called pin. This does not influence the entire surface, but appears only locally; Its occurrence is likewise to be attributed to an excessive extrusion speed with reference to the aluminium or its alloys, with local tearing or disintegration of the oxide layer.

During the operation of a tool, through the presence of atmospheric oxygen, aluminium oxides collect at the downstream end of the working surface of the tool, like a crust surrounding the downstream end of the working surface, while the oxide deposits are promoted with increasing deformation heat in the tool. Byintermittent chipping off of the oxide layer, the broken off part is embodied on or in the surface of the extruded workpiece, with formation of a surface defect other than the hitherto descirbed kind.

For economical use of a press with consideration of a satisfactory surface'a press should therefore be operated with an ingot or billet at ideal temperature and at an extrusion speed at which the surface defects mentioned previously are avoided. From the attempts to optimise the output of existing plant, there has already been an indication to increase the extrusion speed with the billet temperature held unchanged, with an additional removal of the deformation heat arising in the workpiece. As suitable means for additional removal of deformation heat reference is made to the use of water led through passages in the die. The use of water for removal of the deformation heat, however, brings disadvantages with it. For an effective heat removal, raising the extrusion speed to a significant extent, large amounts of water are necessary, which require large cooling passage cross-sections, which lead to a disadvantageous weakening of the cross section of the die. Moreover it is to be observed, that the effectiveness of the removal of heat with increasing time of operation of the tool decreases byreason of the deposits of scale on the passage walls. lt'is also known to envelope the downstream end of a working surface with an inert gas, supplied by lances to the tool, for resisting the formation of a crust-like oxide layer. By these measure the extrusion speed cannot be raised, because no removal of deformation heat results.

The invention starts from this, and has as its object to provide a method of extrusion of workpieces, especially of aluminium alloys, with which the disadvantages sketched above are put aside, and the solution of the problem is characterized in that liquid nitrogen is supplied to the tool and at the beginning of the travel a through the tool the liquid nitrogen is brought into the gas phase. By a preferably explosive increase of the vol,- ume of liquid nitrogen by about 200 times, a large volume transport means is offered to the tool for carrying off the additional deformation heat produced by the increased extrusion speed, without having to bring the drawbacks which appear in conjunction with the known methods.

As has been mentioned already in connection with the known extrusion methods, the formation of an oxide layer at the downstream end of the tool, i.e., at the end of the working surface, is increased by the presence of atmospheric oxygen and by an increased deformation heat in the tool. By thetotal displacement of the atmospheric oxygen the formation of the oxide layer can suitably be avoided, so that with the optimum removal of heat an additional increase of extrusion speed with tolerance of 'an increased tool temperature becomes possible. Accordingly theinventioncan be advantageously embodied in that gaseous nitrogen is directed from the tool in the direction towards the downstream end of the tool.

The device for carrying out the method is characterized by effective removal of the additional deformation heat arising in the die from the increased extrusion speed, in that a regulating valve is present which cooperates with a channel-like recess, and is adjustable to a deformation heat to be removed. According to the invention liquid nitrogen is supplied to the tool and at the beginning of flow through the tool the liquid nitrogen is brought into the gas phase. To provide a control valve for the liquid nitrogen, adjustable to the deformation heat to be removed, is desirable because thereby an optimum supply of gaseous coolant is adjustable and one can avoid that nitrogen flows through the tool while still liquid, which would remove a smaller amount of heat from the tool, quite apart from the fact that such a condition of the coolant would disadvantageously influence the effectiveness of the method.

For further use of the expanded coolant the tool is in addition advantageously so formed that passages are I provided which lead out from the channel-like recess FIG. 3 a section through the tool according to FIG.

FIG. 4 a detail for a modified construction according to FIG. 1.

FIG. 5 a seal to be used with the construction according to FIG. 4.

FIG. 6 a further seal for use with the construction ac cording to FIG. 4.

FIG. 1 shows'an extrusion press 10 the press tool of which is operated in accordance with the invention. The extrusion press 10 consists of a crosshead 13 in which are journalled guides 12 for displacement of the hydraulically driven press plunger carrier 14. Between the crosshead 13 and the press plunger carrier 14 there is a tool slide 15 fixed on the crosshead 13, on which is mounted a tool 16 which will be described in more detail in connection with FIG. 2. A receiver 17 abuts against the tool 16, while by means of the press plunger 18,, metal 19 is driven into the tool for formation of a workpiece 20, for example in the form of an extruded bar. In a vacuum-insulated container 21 there is liquid nitrogen or a similar, preferably inert, liquefied gas. A hose 22 connects the container 21 with the tool 16 for supplyof the coolant. In the direction of flow of the liquid nitrogen there is inserted into the hose 22 first a regulating valve 23, then a safety valve 24, and thereafter a magnetic valve 25. By means of the regulating valve 23, the quantity drawn off from the container 21 is adjusted corresponding to the additional deformation heat to be carried off, with observation of a complete conversion of the amount drawnoff into the gas phase in the tool. The safety valve 24 is intendendto satisfy safety requirements. The magnetic valve 25 cooperates with the press plunger or with the extrusion pressure in the receiver 17, in such a way that the magnetic valve 25 opens for supply of coolant only after expiration of the time range of initial ingot or billet deformation, i.e., after reduction of the deformation pressure, released by the commencing flow of the billet, and remains open until the extrusion process is completed and the press plunger 18 is withdrawn for reception of a new billet. The magnetic valve 25 is accordingly effectively opening only in the effective period of extrusion. A delivery table is indicated at 26. FIGS. 2 and 3 show a tool 16 made for employing the method. The tool 16 consists, in the direction of flow of the metal which is flowing through extrusion pressure, of the die 28 which is provided with a mandrel 29 fixed to a bridge not shown, for production of a hollow section. The flowing metal enters the die 28 through entry openings 30 in streams which are divided by the bridge and flows, with joining and welding together of the partial streams, along the working surface 31, out of the die 28 with formation of the desired workpiece 20. The die 28 is in the case shown made in two parts, in that for formation of the outer circumference of the workpiece an insert 32 is provided. The die 28 with insert 32 are set in a holder 33, which abuts through a sealing ring 34 on a pressure ring 35, which in turn is received in a pressure ring holder 36. In this case a channel shaped recess 37 is provided, as shown in FIG. 2, extending annularly in the pressure ring 35, from which passages 38 open near the downstream end of the working surface 31. In the recess 37 open two delivery pipes 39 for production of a uniform removal of heat from the tool 16, and the coolant supplied flows through the outlet opening 40 into the respective cavities 41 and 42 of the pressure ring 35 and pressure ring holder 36, with production of the desired result already described. As FIG. 2 shows, the channel-shaped enlargement 37 opens towards the die 28 with its insert 32, so that the coolant can arrive into contact with the die 28 and the insert 32. Likewise, the passages 38 are made gutter-shaped. The shape, open on one side, for the recess 37 and passages 38 has the advantage, that the path for coolant can be made what is best from flow considerations, together with a simplified introduction into the pressure ring 35. The tool construction according to FIGS. 2 and '3 shows a best construction. If for example the die were integral, i.e., made without insert 32, then the channel-shaped recess 37 can be made in the recess 43 which receives the die 28, for example by internal piercing on a lathe. Upon insertion of the die in the recess 43 of the holder 33 there thus arises an annular passage running round the die from which bores can be made in the direction towards the downstream end of the working surface 31. Accordingto FIG. 1 the tool 16 is connected to the container 21 by a hose 22, which permits displacement of the tool slide 15 with the tool 16. For a rapid exchange of tools, and to avoid losses, the feed of coolant to the tool is made differently, in accordance with FIG. 4. The hose described in connection with FIG. 1 is here replaced by a heat-insulated pipe 44 which is permanently connected to the press and which opens beneath the tool slide 15 into the tool slide support 45. A bore 46 extends into the tool slide 15 and at its outlet end there is a connection 47 provided to the tool 16, which will be explained in more detail in connection with FIG. 6. The pipe 44 is attached to a prolongation welded to the tool slide carrier 45, which is provided with a bore 48 through it. Between the tool slide support and the tool slide 15, there is a plate 49 shown in FIG. 5, preferably of a non-ferrous metal such as copper, which is fastened by means of bolts 50 to the underside of the tool slide 15. The plate 49 has a bore 51, which is provided with a countersink 52 at its end facing the tool slide. The countersink 52 has as its object a sufficient flow cross section, in the case of reduction of the inlet side of the bore 46 to the flow passages 48-.

At the downstream end of the bore 46, there is the connection 47 shown in FIG. 6 between the tool 16 and the tool slide 15, consisting of the head 53 inserted in the tool 16 and the support 54 provided in the bore 46. The head 53 carries at one end a thread for fixing the head 53 in the tool 16, which is adjacent to a hexagon 55. The face of the hexagon away from the thread carries a spherical extension 56, A bore 57 for conveying the coolant penetrates the head 53. The support 54 consist of a shouldered bush 58, which engages in a tube 59 with a closure wall 60. The shouldered bush is inserted in the bore 46 and aspring 61 urges the shouldered bush 58 and the pipe 59 apart. In the closure wall 60 there is a bore 62, the countersink 63 of whichserves for sealing reception of the spherical-shaped extension 56. The support 54 is inserted so far into the bore 46, that upon support of the tool 16 onthe tool slide the head 53 is brought into sealing engagement on the support 54 in the connection 47 to the bore 46.

By this form of construction the coolant supply is continuously connected with the press 10, and thus all the pipes can be made thermally insulated. Timeconsuming manual operations for changing the tools disappear, for these are connected to the coolant supply by support on the tool slide.

It is also advisable to allot measurements differing from one another to thecoolant passages, consisting of the passages 38 and the channellike recess 37, e.g., so that the cross sections of the passages 38 are larger than that of the channel 37 which can surround the working surface, or the other way round. In addition a supplementary recess can be provided at the coolant entry into the die, that is to say always in the neighbourhood of the beginning of the channel 37, which forms part of the channel 37, to assist the complete vaporisation of the coolant at the entry to the tool. This recess can however also be located at the places where the radially extending supply passages 39 open into the channel-shaped recess 37. The reason for allowing differing measurements for passages 38 and recess 37 is to influence flow conditions of the gas which maintains to increase its volume while flowing through the die.

In order to avoid gasflow obstructions the crossection of passes 38 is larger than that of recess 37.

In case it is desirable to obtain a high gas speed at the delivery end 40 of the passages 38 one will make the cross-section of the passages smaller than that of recess 37.

We are comparing always the crossection of each passage 38 with the crossection of recess 37 and mean preferably the width. Naturally in the same way also the depth may be considered.

We claim:

-l. A method for extruding workpieces, for example made of aluminum alloys, by means of a tool through which a coolant is circulated comprising the steps of supplying a deep cold liquified inert gas to the tool and bringing the liquified gas to the gaseous state at the beginning of the flow thereof through the tool.

2. The method according to claim 1 further comprising the step of removing the gas from the tool in a direction towards the downstream end of the tool. 

1. A method for extruding workpieces, for example made of aluminum alloys, by means of a tool through which a coolant is circulated comprising the steps of supplying a deep cold liquified inert gas to the tool and bringing the liquified gas to the gaseous state at the beginning of the flow thereof through the tool.
 2. The method according to claim 1 further comprising the step of removing the gas from the tool in a direction towards the downstream end of the tool. 